TV Repair Questions? Ask a TV Technician
Have original remote...but no pic.
Hit the MENU button...nada.
The red LED flickers indicating it got a command from remote...but nuttin on the screen.
k. will get back shortly
No sign of life at all.
Completely dark. Waited till sound from channel came on....so I know the cable box is transmitting and TV actually receiving the Channel data. Won't/can't show video.
TV is 3 yrs old i think.
Let me check.
Gotta get mentally prepared for deeper troubleshooting.
I'm not stable right now.
Bruins in Stanley Cup Final game 6 tomorrow night!
Plazma layin nice and flat.
Got the back panel off.
Lookin a lot easier to work on than the DLP Sony.
Been runnin for 30 minutes.....nuttin hot at all.
Looked around for fried Caps. No signs.
OK. 10.2V on VS. VA is zero. Ouch!
With cable disconnected: VS=8.6v VA still zero
No Cable: VS= 8.6V VA =zero
With cable back in: VS=10.2V VA=zero
Digital meter (still make analog?).
I am 100% certain of these measurements.
Chasis to the corresponding TP's.
On the left we have a large circuit board(PCBA).
Is this what you refer to as the main board?
Between that board and the power supply in the middle there's nothing....just a connector bringing VA and VS over....same cable I disconnected.
No file attachment option here. Only insert.
After insert Reply failed.
Have an email I can send it to?
Not much easier.
VS_ON does pop to 3.2V for a very short time then back to zero during power up.
PS_ON does not change from zero.
Not sure if you got my last response.
"VS_ON does pop to 3.2V for a very short time then back to zero during power up.
PS_ON does not change from zero."
Where do we go from here?
A few questions:
What should VS and VA be?
What functions do VS and VA support?
Want to be sure the symptoms of no Screen but lots of other electronics working just fine(ie: channels change and we get audio) are consistant with these voltages being out of whack.
Also, VS-ON only measured 3.2V for a very brief moment. Is it a control signal or power supply?
Well. I might be qualified.
Can you tell me where to get a schematic...and PCBA drawing?
Know how to get a schematic and PCBA drawing?
New PS board came in yesterday.
Installed but sadly nothing changed.
No. But we ran that test before though
Ok. This needs clarification.
If you recall previously, the signal names you gave do not match up with what's on the boards.
Closest I can find is PS_ON and VS_ON.
PS_ON goes to 2 cables.
VS_ON goes to 1 cable.
So, first test, loading test: power up normally then disconnect what cables? All of them?
Second test: measure PS_ON or VS_ON while TV is powered up?
I think most of the confusion is from your 2nd to last response where you asked me to "disconnect YSUS and ZSUS".
I have definitely found VS and VA...for sure.
But YSUS and ZSUS???
1) I am looking for clarification that these correspond to PS_ON and VS_ON.
2) When you said to "disconnect" them it also presented some confusion.
So back to my questions.
After normal power up I know VS=10.6V and VA=0.
At this point do you want me to disconnect ALL the cables to see if the loading problem is on another board? Or what specific cable would you like me to disconnect?
>>I think most of the confusion is from your 2nd to last response where you asked me to "disconnect YSUS and ZSUS".<<
YSUS and ZSUS are circuit boards, not voltages. Maybe that's where the confusion is. Standing behind the TV, the YSUS (y-sustain) is the large board on the left hand side of the TV. It's on the other end of the connector I outlined in green, above.
The ZSUS is on the right hand side. It looks the same as the YSUS but is about half the size.
>>I am looking for clarification that these correspond to PS_ON and VS_ON.<<
These are small voltages sent from the logic or main board, to the power supply. They'd be present during the power on sequence only, and would disappear shortly thereafter. These voltages tell the power supply to create its non-standby voltages (e.g., VS and VA).
OK. That helped.
I think VS and VA collapse shortly after coming up.
If, after normal power up, I disconnect ZSUS and then reconnect it, shortly after reconnecting it, I measure voltages up to 200V but then it is quickly dropping and eventually settles back to that 10V range.
I have never measured anything but zero for VA, yet right after reconnecting ZSUS it actually measured over 10V and also was slowly decaying.
NOTE: with ZSUS disconnected, voltages don't come back. It's only after reconnecting it that I see large voltages that decay.
This is excatly what I did when I reported my last results.
I powered the TV.
Didn't move particularly fast to make the voltage measurements.
Noticed that VS was around 19V and slowly decaying and eventually settled down to around 10V. VA was zero.
I then disconnected YSUS and ZSUS: Voltages didn't change.
Reconnected YSUS: no change.
Reconnected ZSUS: VS large and decaying until eventually got back to around 10V.
Disconnect ZSUS ONLY: no change
Reconnect ZSUS: 200V and decaying quickly